The present invention relates to an electric resistance welding and, in particular, to a spot welding gun (including a C type and an X type), a spot welding machine of a stationary type, a projection welding machine, and a resistance seam welding machine; and, in particular, to a resistance welding machine in which a linear guide is used in a guide mechanism of a press type for opening and closing an electrode tip on the movable side thereof, and various unit parts of the present resistance welding machine individually unified according to the functions of the welding machine are assembled together with a common base or the rail main body of a linear guide as the reference thereof, and a method for assembling such resistance welding machine.
As a conventional spot welding gun, there is known a spot welding gun which uses a linear guide system in a movable-side electrode tip drive mechanism. A conventional spot welding gun of this type is disclosed, for example, in the specification and drawings of Japanese Patent Unexamined Publication No. Hei. 10-34346.
In the conventional spot welding gun of this type, a second gun arm disposed so as to correspond to a first arm gun fixed to a gun main body is driven along the gun main body by a pressure drive mechanism comprising a ball screw, a sliding nut, a linear guide and servo motor each disposed within the gun main body, two lap plates (works) are held together by and between two electrode tips, and a pressing force necessary for welding is given to the two electrode tips as well as a welding current is passed through the two electrode tips to thereby heat and weld together the respective welding portions of the two lap plates (works).
According to the conventional spot welding gun of this type, when compared with the conventional welding guns that have been used so far, the interfering portions thereof are decreased to thereby reduce restrictions on the moving passages and welding positions thereof. Thanks to this, according to the sizes and shapes of members to be welded, the gun arm can be recomposed freely each time the stroke thereof varies.
However, since the conventional spot welding gun of this type is structured such that the pressure drive mechanism is disposed in the inside portion of the gun main body integrally therewith, when assembling a welding transformer and an equalizing device into the spot welding gun. That is, the current assembling method finds it difficult to assemble or recombine various units according to the functions of the welding gun.
The present invention aims at eliminating the drawbacks found in the above-mentioned conventional welding machines.
In solving the above problems, according to the invention, there is provided a method for assembling a resistance welding machine, the method comprising the steps of:
providing a common base of the resistance welding machine;
mounting fixedly and detachably an arm onto the common base with a first detachable securing member, the arm including an electrode tip of the resistance welding machine;
mounting fixedly and detachably a drive unit onto the common base with a second detachable securing member, the drive unit driving a mating electrode tip mating with the electrode tip; and
mounting fixedly and detachably a welding unit onto the common base with a third detachable securing member, the welding unit including at least one of a welding transformer which can apply a secondary current to the resistance welding machine and a gun bracket for supporting the resistance welding machine onto a robot.
According to the above-mentioned method as set forth in the present invention, when compared with the conventional spot welding gun, instead of forming a pressure drive mechanism in the inside portion of a gun main body integrally therewith, the gun arm, welding transformer, drive unit and the like can be mounted and removed individually as a unit with the common base as the reference thereof. Thanks to this, not only there is eliminated the need for new design of the structure of the spot welding gun, but also the units standardized according to functions of the spot welding gun can be assembled or recombined easily according to uses.
In the above-mentioned method according to the present invention, it is preferable to further comprises the steps of:
mounting fixedly and detachably an equalizing unit onto the common base with a fourth detachable securing member, the equalizing unit has one of a function for positioning the mating electrode tip relative to the electrode tip and a function for correcting a moving amount of the mating electrode tip relative to the electrode tip.
Accordingly, the equalizing unit can be easily mounted and removed according to the variations of the welding machine similarly to the above-mentioned unit parts.
The above-mentioned drawbacks can be solved by a resistance welding machine according to the present invention comprising:
a common base;
an arm including an electrode tip of the resistance welding machine, the arm being fixedly and detachably mounted onto the common base by a first detachable securing member; of an electric pressure type
a drive unit driving a mating electrode tip mated with the electrode tip while the electrode tips are subjected to an electric pressure, the drive unit being fixedly and detachably mounted onto the common base by a second detachable securing member;
a welding unit including at least one of a welding transformer which can apply a secondary current to the resistance welding machine and a gun bracket for supporting the resistance welding machine onto a robot, the welding unit being fixedly and detachably mounted onto the common base with a third detachable securing member.
In the resistance welding machine, it is advantageous that the drive unit comprises:
a ball screw shaft,
a nut linearly moved in accordance with a rotation of the ball screw shaft and supporting the mating electrode tip, and
a unit main body for rotatably supporting the ball screw shaft and guiding the linear movement of the nut while a plurality of balls are rolled between the nut and the unit main body.
According to the welding objectives are satisfied:
(1) High assembling accuracy can be obtained easily;
(2) Because the rigidity of the drive unit can be enhanced and the weight thereof can be reduced, the followability thereof can be enhanced in the welding operation;
(3) Assembly and maintenance can be facilitated;
(4) It is possible to omit an electrode rotation stop mechanism which is necessary when a guide center and an electrode pressure center are present at offset positions; and
(5) As to the drive unit, mass-producible commercial standardized products can be used, which makes it possible to reduce the cost of the drive unit to a great extent.
Further, according to the welding machine, since the two sides of the common base can be used as the mounting reference, according to the variations of the welding machine, the equalizing unit, gun arm, and welding transformer can be mounted and removed as well as replaced as a unit easily. And, they can be manufactured with the weight and size thereof reduced.
In the above-mentioned welding machine, it is also preferable to include:
an equalizing unit having one of a function for positioning the mating electrode tip relative to the electrode tip and a function for correcting a moving amount of the mating electrode tip relative to the electrode tip, the equalizing unit being fixedly and detachable mounted onto the common base with a fourth detachable securing member,
wherein the equalizing unit includes an air circuit for canceling a load corresponding to a dead weight of the resistance welding machine.
In the above-mentioned welding machine, it is further preferable that the air circuit is provided with a balancing cylinder for executing at least one of an air pressure increasing and decreasing operation and a direction switching operation, to thereby obtain a weight balance of the resistance welding machine.
According to this, the equalizing operation and the balancing operation are not executed according to the program stored on the robot side, but these operations are carried out by using an independent equalizing mechanism and a balancing air pressure circuit. Therefore, there is eliminated the need to increase the number of robot control shafts and add software for allowing the fixed-side electrode tip to touch softly or approach the work; and, the one-shaft servo spot gun may be simply added to the current number of robot control shafts. This makes it possible to simplify the structure of the welding machine as well as reduce the installation cost thereof.
Furthermore, it is also preferable that the common base is formed of aluminum based material.
According to this, the weight reduction of the common base can be facilitated, thereby being able to reduce the weight load to be carried by the robot wrist.
The above-mentioned drawbacks can also be solved by a spot welding machine comprising:
a gun arm having an electrode tip;
an electrode drive unit having
a ball screw shaft,
a nut linearly moved in accordance with a rotation of the ball screw shaft and supporting the gun arm, and
a guide rail body extending in parallel with the ball screw shaft and guiding the linear movement of the nut while a plurality of balls are rolled between the nut and the unit main body;
a holding member holding a mating electrode tip mated with the electrode tip, the holding member being fixedly and detachably mounted onto the guide rail body with a detachable securing member; and
a welding unit including a welding transformer which can apply a secondary current to at least one of the resistance welding machine and a gun bracket for supporting the resistance welding machine onto a robot, the welding unit being fixedly and detachably mounted onto the guide rail body with a detachable securing member,
wherein an electric pressure between the electrode tips are generated by the electrode drive unit.
According to the welding machine, when compared with the conventional welding gun in which a drive mechanism is formed in the inside portion of a gun main body integrally therewith, with the rail main body as the reference, the gun arm, gun bracket, equalizing unit, welding transformer and the like can be mounted individually as a unit. This eliminates the need for new design of the structure of the robot gun with a welding transformer incorporated therein. Also, in this case, the above-mentioned common base can be omitted, which can facilitate further reduction of size and weight of the welding machine.
In addition, in the above-mentioned welding machine, it is advantageous that the holding member is one of a point holder including the mating electrode tip and a gun arm member including the point holder.
Since the gun arm is directly connected to the output terminal of the welding transformer, at least one side secondary bar can be omitted. This makes it possible to reduce the number of parts, the number of man-hours for assembling, and the weight of the welding machine.
Moreover, the above-mentioned drawbacks can be solved by a spot welding machine according to the present invention, the ball screw shaft is combined into the nut block of a linear guide and the ball screw shaft is driven by a motor to thereby allow an electrode tip movable by the nut block to generate a torque for obtaining pressure necessary for welding, wherein said ball screw shaft has a right screw and a left screw, a nut block N1 for a right screw and a nut block N2 for a left screw are combined into said ball screw shaft respectively, two mutually opposing gun arms are respectively mounted on said nut blocks N1 and N2, and two mutually opposing electrode tips respectively supported by said gun arms can be driven simultaneously from both sides by a single electric motor.